In recent years, in reflection of the need for higher-speed communication and more compact communication devices, there has been an increasing demand for a lens array in which a plurality of lenses are arranged in parallel, as a compactly structured optical component effective for actualizing multichannel optical communication.
This type of lens array is capable of multichannel optical transmission achieved by a plurality of light-emitting elements (such as vertical cavity surface emitting lasers [VCSEL]) and a plurality of optical fibers being optically coupled, and multichannel optical reception achieved by a plurality of optical fibers and a plurality of light-receiving elements (such as photodetectors) being optically coupled. Furthermore, in addition to usage such as this, usefulness of the lens array is expected to further rise in the field of optical communication, such as through application to optical waveguides. In accompaniment, freedom of design of the lens array is expected to further widen.
Many of such lens arrays include convex-shaped lens faces. However, in some instances, concave-shaped lens faces are required depending on the light-beam shape to be formed, the light-beam diameter to be achieved, product dimensions, and the like (refer to, for example, Patent Literature 1).    Patent Literature 1: Japanese Patent Laid-open Publication No. 2003-121615